Dynamics of action of bisphenol as radical-scavenging antioxidant against lipid peroxidation in solution and liposomal membranes

Bisphenol A increases BeWo trophoblast survival in stress-induced paradigms through regulation of oxidative stress and apoptosis

Bisphenol A (BPA) is ubiquitous in the environment and is reported to be present at high concentrations in placental tissue, where its presence raises concerns over its potential to disrupt placental function. This report investigates how BPA interferes with the survival of human choriocarcinoma BeWo cells (a model of placental trophoblasts) under stress-induced paradigms reminiscent of pathways activated in placental development. These include conditions that promote oxidative stress (glutathione depletion) and apoptosis (serum withdrawal) or mimic hypoxia (HIF-1α accumulation via dimethyloxalylglycine treatment). Treatment of BeWo cells with BPA during stress-induced paradigms led to a consistent and significant increase in cell viability, with a concomitant increase in glutathione levels and a reduction in apoptosis. Assessment of the antioxidant capacity of BPA revealed its ability to quench reactive oxygen species and reduce the levels generated during glutathione and serum depletion. BPA was also able to reduce the activation of the antioxidant response element (ARE) through mediation of its activators, nuclear factor erythroid related factor family members (Nrf's). Indeed, the expression and nuclear translocation of Nrf2 (an important ARE activator) were impaired by BPA, while Nrf1 and Nrf3 expression levels were increased. Furthermore, BPA increased the levels of the anti-apoptotic proteins (Bcl-2 and Hsp70) and decreased HIF-1α levels during stress-induced conditions. Together, these results indicate that BPA inhibits trophoblast cell death under conditions of cellular stress. This could have implications on placental trophoblasts during development.

Influence of α-tocopherol and α-lipoic acid on bisphenol-A-induced oxidative damage in liver and ovarian tissue of rats

Bisphenol A (BPA) is a commonly used material in daily life, and it is argued to cause oxidative stress in liver and ovarian tissue. α-Lipoic acid (ALA) and α-tocopherol (ATF), two of the most effective antioxidants, may play a role in preventing the toxic effect. Therefore, the purpose of this study was to examine the beneficial effects of ALA, ATF, and that of ALA + ATF combination on oxidative damage induced by BPA. Female Wistar rats were divided into five groups (control, BPA, BPA + ALA, BPA + ATF, and BPA + ALA + ATF). BPA (25 mg/kg/day), ALA (100 mg/kg/day), and ATF (20 mg/kg/day) were administered for 30 days.  The levels of serum aspartate aminotransferase (AST) and alanine aminotransferase (ALT), liver malondialdehyde (L-MDA) and glutathione peroxidase (L-GPx), and ovarian malondialdehyde (Ov-MDA) and nitric oxide (Ov-NO) were significantly higher in the BPA-treated groups compared with the control group. The levels of AST and ALT decreased in the BPA + ALA, BPA + ATF, and BPA + ALA + ATF groups compared with the BPA group. Similarly, BPA + ALA or BPA + ATF led to decreases in L-MDA and Ov-MDA levels compared with the BPA group. However, the BPA + ALA + ATF group showed a significant decrease in L-MDA levels compared with the BPA + ALA group and the BPA + ATF group. The levels of L-GPx decreased in the BPA + ATF and the BPA + ALA + ATF groups compared with the BPA group. The administration of ATF and ALA + ATF significantly decreased the Ov-NO levels.  This study demonstrates that BPA causes oxidative damage in liver and ovarian tissues. ALA, ATF, or their combination were found to be beneficial in preventing BPA-induced oxidative stress.

Ethanolamine plasmalogens prevent the oxidation of cholesterol by reducing the oxidizability of cholesterol in phospholipid bilayers

The aims of the present study are to establish an appropriate system for assessing the oxidizability of cholesterol (CH) in phospholipid (PL) bilayers, and to explore the effect of ethanolamine plasmalogens on the oxidizability of CH with the system, through comparing with those of choline plasmalogens, phosphatidylethanolamine, and antioxidant alpha-tocopherol (Toc). Investigation of the effects of oxidants, vesicle lamellar forms, saturation level, and constituent ratio of PLs in vesicles on CH oxidation revealed the suitability of a system comprising unilamellar vesicles and the water-soluble radical initiator 2,2'-azobis (2-amidino-propane) dihydrochloride (AAPH). As CH oxidation in the system was found to follow the rate law for autoxidation without significant interference from oxidizable PLs, the oxidizability of CH in PL bilayers could be experimentally determined from the equation: k (p)/(2k (t))(1/2)=R (p)/[LH]R(i)(1/2) by measuring the rate of CH oxidation. It was found with this system that bovine brain ethanolamine plasmalogen (BBEP), bovine heart choline plasmalogen, and egg yolk phosphatidylethanolamine lower the oxidizability of CH in bilayers. Comparison of the dose-dependent effects of each PL demonstrated the greatest ability of BBEP to reduce the oxidizability. A time course study of CH oxidation suggested a novel mechanism of BBEP for lowering the oxidizability of CH besides the action of scavenging radicals.

Antioxidant effect of capsaicin on lipid peroxidation in homogeneous solution, micelle dispersions and liposomal membranes

The antioxidant activity of capsaicin (CAP) was measured in the oxidation of methyl linoleate (ML) in homogeneous solution, of ML micelles in aqueous dispersions and also of soybean phosphatidylcholine liposomal membrane, and was compared to that of alpha-tocopherol (alpha-TOH) which is one of the most important antioxidants in vivo. The reactivity of CAP toward galvinoxyl (a model phenoxyl radical) in acetonitrile solution was found to be much smaller than that of alpha-TOH, suggesting that the radical scavenging activity of CAP is much weaker than that of alpha-TOH. In fact, in homogeneous acetonitrile solution where the antioxidant activity is determined primarily by the chemical activity of the antioxidant toward peroxyl radicals, CAP inhibited the oxidation of ML much less efficiently than alpha-TOH and a clear induction period was not observed. The antioxidant activity of CAP was found to be about 60 times smaller than that of alpha-TOH in homogeneous solution. However, in micelle oxidation, the difference in antioxidant activity of the two antioxidants was much smaller than in homogeneous solution. Furthermore, in the membrane, CAP inhibited the oxidation almost as effectively as alpha-TOH. These results suggest that CAP can act as an antioxidant in the biomembrane.